Electrical resistance alloy



ing in the ratio range of 1 to 1 Patented Feb. 29, 1944 2,343,040ELECTRICAL RESISTANCE ALLOY Victor 0. Allen, Madison and Joseph F.Polak, Newark, N. J., assignors to- Wilbur B. Driver Company, Newark, N.J., a corporation of New Jersey No Drawing. Application December 18,1942,

' Serial N0. 469,466

(Cl. IE-.434)

6 Claims.

This invention relates to electrical resistance alloys and moreparticularly to the electro-magnetic type of high temperature electricalresistance alloys known in the art as iron-chromiumnickel alloys whichcontain from 10 to.30% Cr, from to 50% Fe with the balance of the alloyconsisting of Ni.

One object of the present invention is to increase the electricalresistance of said alloys and to lower the temperature coeflicient ofresistivity thereof, thereby to obtain a more efiicient resistorelement.

Another object is to provide an improved high temperature electricalresistor alloy and resistor element made therefrom.

Still another object is to improve the electrical resistance and thetemperature coefficient of resistivity characteristics ofiron-chromium-nickel electrical resistance alloys.

Other objects will be apparent as the invention is more fullyhereinafter disclosed.

in accordance with these objects we have discovered that aluminum andcopper additions in amounts ranging from 1.5,to 8% Al and 1.5 to

1 4% Cu are effective in obtaining an increase in the electricalresistance and a decrease in the temperature coefficient of resistivity.in ironchromium-nickel alloys of the high temperature resistor type.

As one specific embodiment of the present invention, the same will bedescribed in connection with an alloy containing Fe 25%, an'ce Ni. Thialloy is old and well known in the art, per se, and is widely used as .ahigh tern perature resistor element in rheostats, electric heatingelements, etc.,- where operating temperatures as high as 1850" 5'. maybe desired. This alloy is known to have an electrical resistance ofabout 675 ohms per C. M. F. and a temperature coefficient of about.00022 per ohm per de gree centigrade.

We have found that aluminum and copper additions to this alloy in theranges 1.5 to 8.0% and 1.5 to 4.0% respectively with the Al and Cu bevup to 2 to 1, increases the electrical resistance of the alloy from 6'75ohms per C. M. F. up to avalue closely approximating 1000 ohms per C. M.F. and lowers the temperature coefficient of resistivity from the value.00022 to about .000094, without otherwise being deleterious tp thephysical and chemical properties of the alloy, such as, its hot and coldworkability, slstance, or

its normal resistance to corrosive attack.

Cr 15%, balits high temperature oxidation re- As specific examples ofthe improved alloy of and Cu on the electrical resistance andtemperature coefficient of resistivity of an alloy containing 25% Fe,15% Cr, balance Ni, is indicated in the following table:

AlloyNo. Al Cu Fe Cr Ni E.R./C.M.F. T.C.

1 25 15 675 .00022 2 2s 1s 57 752 .000141 a 25 1s 53 801 .000133 4 25 1552.5 826 .000128 5 25 15 52.0 831 .000108 6 25 15 48.0 950 .00008 In theabove table E. RJC. M. F. is an abbreviation of electrical resistanceper circular mill foot at 20 C. and 'I. C. is an abbreviation oftemperature coeflicient of resistivity" which is usually determined overa range of temperatures below 300 0.

As indicated in the table the addition of Aland Cu in amounts rangingfrom 1.5 to 8% A! and 1.5 to 4% Cu, in substitution for an equivalentamount of Ni, markedly increases the electrical resistance of the alloyand at the same time markedly lowers the temperature coeflicient orelectrical resistivity. With increasing Al and Cu content, theelectrical resistance increases and the temperature coefiflcient ofresistivity decreases. Cu additions in excess of about 4% to the alloy,however, detrimentally effects the hot working properties of the alloyand Al additions in excess of 8% detrimentally efl'ect both the hot andcold workability of the alloy. However, with copper 4% and Al 0%, thehot and cold workability of the alloy is such that it may bemechanically reduced to the smallest diameter wires normally employedwith alloys of this type, for example, to .001 inch, and, withappropriate care, to sizes as small as..0007 inch, if desired. In theabove table, the size at which the above values were determined was.0055 inch diameter. In the above specific alloy, the chromium contentmay vary within the range'10-30% with corresponding increase or decreasein the nickel content without departure from the present in vention, butwith corresponding variation in the .electricalresistance andtemperature coefiicient of resistivity values as one skilled in the artwill recognize. Such alloys, however, will show the same trend ofincreasing and decreasing "E. RJC. M. F. and fT. C. values,respectively, that are indicated in the above table.

Ironvariations within the range 5 to 50% in the alloy of the presentinvention effect primarily the operating temperature of the alloy andsec-' ondarily efiect the total A1 and Cu that may be added withoutdetrimentally effecting the hot and As the iron increases to 50% thetotal Al and Cu that maybe added to the alloy without detrimentallyefiecting thehot and cold workability increases to about 14%, with A1about 10% and Cu not over about 4%. As the iron decreases to 5% thetotal Al and Cu that may be added to the alloy without detrimentallyefiecting the hot and perature coeflicient of resistivity below .00022,

cold workability of the alloy decreases to about 9% with Cu about 3% andAlabout 6%.

As another specific example of the present invention an alloy containingCr 13%, Fe 6.5%,

an E. R./C. M. F. of about 795 ohms and a T. C. of about .000034 ohm,with an operating temperature of about 2000" F.

Having hereinabove described the present invention generically andspecifically and given sev- A1 5%, Cu 3%, balance Ni, has been found tohave eral specific examples thereof, it is believed apsaid alloyconsisting of Cr 10 to 30%, Fe 25%, A1 1.5 to 8.0%, Cu 1.5 to 4.0%, withthe Al to Cu within the ratio range of 1 to 1 and 2 to 1, balance Ni.

3. An electrical resistance alloy having a temperature coeflicient ofresistivity below .00022, said alloy consisting of Cr 15%, Fe 25%, A11.5 to 8%, Cu 1.5 to 4%, balance Ni.

4. An electrical resistance alloy having a temperature coefflcient ofresistivity of about .000141, said alloy consisting of Cr 15%, Fe 25%,A1 1.5%, Cu 1.5%, balance Ni.

5. An electrical resistance alloy having a temperature coefiicient ofresistivity of about .000128, said alloy consisting of Cr 15%, Fe 25%,A1 4.5%, Cu 3%, balance Ni.

6. An electrical resistance alloy having a' temperature coefiicient ofresistivity of about .00008, said alloy consisting of Cr 15%, Fe 25%, Al8%, Cu 4%, balance Ni.

VICTOR O. ALLEN.

JOSEPH F. POLAK.

